This invention relates to a control unit responsive to gas pressure and a method of providing control signals. More specifically, this invention relates to an altitude compensating bleed valve and a method for controlling turbine speed for an internal combustion engine.
In a turbocharger system for supplying air under constant pressure to an internal combustion engine, the output of the turbocharger must be adjusted for changes in altitude or density of the gases provided to the turbocharger.
The turbocharger, as a method of pressurizing the air supply to an engine, comprises a centrifugal compressor which is generally driven by a turbine powered by the engine exhaust gases. Normally, as engine speed is increased providing increased exhaust gases, the turbine speed also increases, which in turn operates the compressor at increased speed providing a higher density of air supply to the engine. In order to regulate turbocharger operation, all or a portion of the exhaust gases may be diverted around the turbine. Such a device is commonly called a wastegate bypass valve.
Wastegate bypass valves are well-known in the prior art. Typically, a pressure sensitive device, in response to changes in the output of the compressor (sensed within the compressor or between engine and compressor as either total or static pressure or a value in between), will open and close the wastegate bypass valve through hydraulic or electrical means as a system to prevent turbocharger overspeed. Some turbocharger control systems require manual operation of the throttle to initiate the system or control its use.
Control systems not requiring manual operation that compensate for altitude by adjusting turbocharger speed typically consist of similar complex mechanical and hydraulic sub-systems. These devices compare the turbocharger output with ambient air, the difference providing the input that controls the wastegate.
The present invention overcomes the problems and disadvantages of the prior art by providing an improved and simplified pneumatically controlled wastegate for maintaining a constant intake manifold pressure by varying the turbocharger speed for changes in altitude.